The cooling of stored articles such as food products is conventionally realized by using a heat storage agent. A typically used heat storage agent has a melting point below 0° C., and for example, is first cooled at a low temperature in the order of −25° C. in a freezer and then removed for use. When freezing the heat storage agent, the heat storage agent is typically frozen in an environment that is at least 10° C. lower than its freezing point, and even a heat storage agent having a melting point in the vicinity of 0° C. is frequently frozen in an environment of −25° C. As a consequence, when the heat storage agent is used immediately after having been removed from a freezer, the stored article will be cooled to below 0° C.
Stored articles that are cooled using heat storage agents in this way include such articles as specimens that are preferably cooled to the level of 2-8° C. and that are preferably not cooled to 0° C. or below. When such a stored article is to be kept cool, the heat storage agent is first removed from the freezer and then left for 30 minutes to three hours at room temperature or in a refrigerator to raise the temperature of the heat storage agent to the melting point. However, removing the heat storage agent from the freezer and leaving it out for a certain time after removal is not efficient and does not allow immediate use when its use is desired.
Here, a solution can be considered in which two heat storage agents are used so as not to excessively cool a stored article. In this case, if two heat storage agents are arranged one over the other and a state is established in which the heat storage agent on the side away from the stored article is frozen and the heat storage agent on the side of the stored article is not frozen, the stored article will be indirectly cooled by the heat storage agent that is frozen by way of the heat storage agent that is not frozen. In this way, the temperature of the stored article will not fall below the freezing point of the heat storage agent that is not frozen, and excessive cooling of the stored article can thus be avoided.
In the opposite circumstances of use in a cold district, the above-described heat storage agent is used to keep a stored article at a desired temperature that is higher than the outside temperature, and in this case, the stored article can be kept at a desired temperature that is higher than the outside temperature by arranging the two heat storage agents superposed as described above and by establishing a state in which the heat storage agent on the side away from the stored article is not frozen and the heat storage agent on the side of the stored article is frozen.
An implement for constant-temperature storage in which two heat storage agents are superposed in this way to keep a stored article at a constant temperature is disclosed in, for example, Patent Document 1 . This constant-temperature storage implement is not only constructed so as to allow installation on the inside wall surface of a storage container that holds the stored article but also includes a double-layer pocket that can accommodate heat storage agents. The stored article can be stored at a desired temperature by placing each heat storage agent in a respective pocket and by establishing a state in which either the heat storage agent on the side of the stored article or the heat storage agent on the side away from the stored article is frozen and the other heat storage agent is not frozen, as described hereinabove.